Chemical Engineering

Statement of the Problem: A notion of “Sustainable development” and the new concept of “Zero emissions” become dominant in the 21^st century. The techniques for NO removal, which are low-temperature, low-cost, environmental-friendly and high efficiency, have become a new research field in the academic and industrial world. Nowadays, due to the special properties of transitional metal element Fe, Fe-based catalysts have become a hot issue on the development of catalysts for SCR of NO. Methodology & Theoretical Orientation: Hematite ore and siderite ore were used as raw material to prepare SCR catalysts for NO removal and NO removal performance was investigated with synthetic flue gas in a fixed bed reactor. Specific surface area analysis, X-ray fluorescence (XRF), X-ray diffraction (XRD), NH₃-temperature programmed desorption (NH₃-TPD) and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTs) were used to analyze the iron ore catalysts and the De-NOx reaction to understand the catalytic performance and mechanism of SCR of NO by NH3. Findings: The siderite catalyst calcined at 450°C was mainly composed of γ-Fe₂O₃ and α-Fe₂O₃. The experiments of catalytic activity on SCR of NO expressed that the siderite catalyst had an optimal NO removal efficiency and the efficiency was above 96% in the temperature range of 150-300°C at GHSV of 7500 h-1. Conclusion & Significance: Siderite catalysts calcined at 450°C showed a good performance of SCR of NO by NH3 at low temperatures. This catalyst had developed pore structure and a big specific surface area. The adsorbed NO₂ would enhance the adsorption and conversion of NO on the siderite catalyst surface at the low-temperature window. Meanwhile, there were a variety of Lewis acid sites to enhance the adsorption of NH3 and NO on the surface of siderite catalyst by both of L-H and E-R mechanism at low temperatures.